REGULATION OF THE FLOW OF BLOOD 189 



so reach the artery below the cut. When capillaries are 

 cut, a new set is produced to take their place. 



324. Effect of tight bands. A tight band will obstruct the 

 flow of blood in the veins, while, unless it is very tight, it scarcely 

 affects the arteries. So the blood freely enters a part through the 

 arteries, but is held back in the veins below the band, until the part is 

 distended with blood, and the proper amount of new arterial blood is 

 prevented 'from entering. As a result the nutrition of the part suffers 

 and slight injuries do not heal readily. The veins swell from the extra 

 amount of blood they contain, and finally enlarge in places, forming 

 what are called varicose veins. Tight garters are common offenders in 

 this respect. 



325. Alcohol and arteries. When a cup of hot coffee 

 is swallowed, the temperature of the stomach and of the 

 blood in its walls is raised. Then nature at once causes 

 the arteries of the skin to become enlarged so that more 

 blood may come in contact with the cool air, and thus give 

 off the surplus heat. Probably in the same manner the heat 

 produced by the destruction of alcohol causes the arteries of 

 the skin to dilate so that they contain an excess of blood. 

 A red face and nose are well-known signs of drinking. 

 This dilation of the arteries is one of the most marked 

 and constant effects of drinking. 



326. Alcohol and the nutrition of cells. Naturally, 

 when a part of the body is at work, its blood tubes 

 become larger, while those of the resting parts become 

 smaller. If the blood tubes of distant parts remain large, 

 there will not be sufficient blood to fill those of the work- 

 ing part, and thus the part will not be able to put forth its 

 full strength. If a part is injured, it cannot get enough 

 extra blood to repair itself quickly. Thus wounds will be 

 apt to heal slowly, while inflammation will be more likely 

 to set in. 



